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991.
DNA/Tannic Acid Hybrid Gel Exhibiting Biodegradability,Extensibility, Tissue Adhesiveness,and Hemostatic Ability 下载免费PDF全文
Mikyung Shin Ji Hyun Ryu Joseph P. Park Keumyeon Kim Jae Wook Yang Haeshin Lee 《Advanced functional materials》2015,25(8):1270-1278
DNA has emerged as a novel material in many areas of materials science due to its programmability. Especially, DNA hydrogels have been studied to incorporate new functions into gels. To date, only a few methods have been developed for fabricating DNA hydrogels, such as the use of complementary sequences or covalent bond. Herein, it is demonstrated that one of the most well‐known plant‐derived polyphenols, tannic acid (TA), can form a DNA hydrogel which is named TNA hydrogel ( T A + D NA ). TA plays a role as a “molecular glue” by a new mode of action reversibly connecting between phosphodiester bonds, which is different from the crosslinking utilizing complementary sequences. TA intrinsically degrades due to ester bonds connecting between pyrogallol groups, causing a degradable DNA hydrogel. Furthermore, TNA gel is multifunctional in that the gel is extensible upon pulling and adhesive to tissues because of the rich polyphenol groups in TA (ten phenols per TA). Unexpectedly, TNA gel exhibits superior in vivo hemostatic ability that can be useful for biomedical applications. This new DNA hydrogel preparation method represents a new technique for fabricating a large amount of DNA‐based hemostatic hydrogel without chemically modifying DNA or requiring the crosslinking by complementary sequences. 相似文献
992.
Enhanced Electrochromism with Rapid Growth Layer‐by‐Layer Assembly of Polyelectrolyte Complexes 下载免费PDF全文
Mengqi Cui Wee Siang Ng Xu Wang Peter Darmawan Pooi See Lee 《Advanced functional materials》2015,25(3):401-408
In this work, a facile method to deposit fast growing electrochromic multilayer films with enhanced electrochemical properties using layer‐by‐layer (LbL) self‐assembly of complex polyelectrolyte is demonstrated. Two linear polymers, poly(acrylic acid) (PAA) and polyethylenimine (PEI), are used to formulate stable complexes under specific pH to prepare polyaniline (PANI)/PAA‐PEI multilayer films via LbL deposition. By introducing polymeric complexes as building blocks, [PANI/PAA‐PEI]n films grow much faster compared with [PANI/PAA]n films, which are deposited under the same condition. Unlike the compact [PANI/PAA]n films, [PANI/PAA‐PEI]n films exhibit porous structure that is beneficial to the electrochemical process and leads to improved electrochromic properties. An enhanced optical modulation of 30% is achieved with [PANI/PAA‐PEI]30 films at 630 nm compared with the lower optical modulation of 11% measured from [PANI/PAA]30 films. The switching time of [PANI/PAA‐PEI]30 films is only half of that of [PANI/PAA]30 films, which indicates a faster redox process. Utilizing polyelectrolyte complexes as building blocks is a promising approach to prepare fast growing LbL films for high performance electrochemical device applications. 相似文献
993.
It is challenging to develop new top‐down approaches to tailor particles into subnanometer size structures on a large scale to further reveal their structure‐dependent physicochemical properties. Here, we demonstrate a non‐conventional, electrochemical, 3D ion‐carving process to tailor particles into subscale flower‐like nanostructures at room temperature. The technology is based on the electrochemical insertion/extraction of lithium ions as a carving “knife” to carve the single‐crystalline particle precursor into higher‐order, flower‐like nanostructures with hexagonal nanopetals as the building units. Our study demonstrates that the morphology of the as‐carved, flower‐like nanostructures can be controlled by the electrochemical parameters, such as the current density and the number of cycles. Particularly interesting is that dramatically different magnetic properties can be achieved depending on the morphology through careful tuning by the electrochemical ion‐carving process. The as‐carved, flower‐like particles may find many important applications, including magnetic nanodevices. Our approach, in principle, is applicable to prepare various kinds of 3D‐structured materials with different compositions. 相似文献
994.
Yong Hui Lee Jingshan Luo Robin Humphry‐Baker Peng Gao Michael Grätzel Mohammad Khaja Nazeeruddin 《Advanced functional materials》2015,25(25):3925-3933
The effect of the presence of unreacted PbI2 on the perovskite solar cells efficiency is reported. N,N‐Dimethylformamide vapor treatment is introduced to study the influence of complete conversion to a power conversion efficiency of the device. It is discovered that the optimized morphology of the PbI2 under layer is essential to form a dense perovskite layer preventing recombination by direct contact between TiO2 and a hole transporting layer, and to increase the charge collection efficiency. The present findings provide an insight into the morphology and growth mechanism of perovskite layer, the correlation between the device performance, and the film deposition process. 相似文献
995.
996.
为了获得混粉雾化快凝中的工艺参数,制备性能优良的球形磁性磨料,提高制备工艺系统的稳定性。通过对雾化快凝工艺的分析,设计了双级雾化器、设计了气力送混粉装置与控制系统、设计了雾化水冷室的结构与冷却供水系统。通过FLUENT流体分析软件,对双级雾化器在不同压力配比下的数值分析,模拟出在上级雾化压力为1.2MPa、下级雾化压力为2.5MPa时得到均匀的速度流场,保证雾化过程的持续性。在现有设计的基础上,通过实验验证了上述设备与工艺参数准确性,制备出了陶瓷硬质磨料颗粒牢固地镶嵌在铁基体表层的球形磁性磨料。 相似文献
997.
998.
通过在真空和氢气环境下的拉伸实验,研究了硼含量对有序态(Fe,Co)_3V合金力学性能和环境氢脆的影响。结果表明,当在有序态(Fe,Co)_3V合金中添加0.02%B(质量分数)时,相对于无硼合金,合金的晶粒尺寸减小了27.5%,合金在真空和氢气中的抗拉强度和延伸率均达到最大值;而当硼含量继续增加时,合金的晶粒尺寸、合金在真空和氢气中的力学性能均保持不变。无硼有序态(Fe,Co)_3V合金在氢气中呈现严重的环境氢脆,当在合金中添加0.02%B后,合金氢脆因子降低了34.4%,合金的断口形貌由完全沿晶断口转变为穿晶和沿晶的混合断口;当合金中的硼含量继续增加时,合金的氢脆因子不再降低,恒定在50%左右,即硼原子只能部分抑制有序态(Fe,Co)_3V合金在氢气中的环境氢脆。 相似文献
999.
以硝酸钇(Y(NO3)36H2O)、硝酸铝(Al(NO3)39H2O)为主要原料,六次甲基四胺作为催化剂,采用溶胶-凝胶法合成Y3Al5O12(YAG)纳米颗粒,并以YAG颗粒为第二相增强材料,通过粉末冶金工艺制备Ag/YAG电接触复合材料;采用X-射线衍射仪(XRD),扫描电子显微镜(SEM),透射电子显微镜(TEM),傅里叶红外光谱(FT-IR)、硬度计、电导率仪等方法对其进行表征。结果表明:在水浴温度为50℃的条件下成功采用sol-gel法合成YAG纳米颗粒,物相纯度高;随着催化剂六次甲基四胺加入量的增加,YAG粉末颗粒粘连在一起,并出现大孔;以YAG为第二相增强材料制备的Ag/YAG电接触复合片材电阻率较低,维氏硬度大于80。 相似文献
1000.
以去离子水为溶剂,低成本工业硅溶胶为硅源,在纯水体系下制备低成本的SiO2纳米多孔材料,使用酸碱两步法催化,添加表面活性剂来降低溶剂的表面张力,从而减少样品在干燥过程中的开裂。最后经过常压老化干燥制备得到 SiO2纳米多孔材料。制备得到的SiO2块体密度为150~400mg/cm3,室内热导率约为0.04~0.07W/(m.K)。这种方法制备的SiO2纳米多孔材料大幅缩减制备成本,采用HCl作为酸性催化剂提高了工业生产安全,将很大程度上推动纳米多孔材料的工业化生产和应用。 相似文献